The invention relates generally to a method and system for adding alloying elements to molten metals. More particularly, however, it relates to the addition of elements which normally dissolve slowly and with difficulty in molten metals, particularly aluminum.
Many different methods have been employed to add alloying elements to molten metals. Conventional methods typically add the elements directly to the melt in the form of a lump, a bar or the like. In some cases, they are added directly to molten metal being tapped into a ladle, and in other cases, they may be placed in the ladle prior to tapping.
Another method for adding alloying elements to molten metals, particularly molten steel, is disclosed in U.S. Pat. No. 3,768,999 to Ohkubo et al. In Ohkubo, alloying is accomplished by feeding a wire rod into the molten metal. The rod is coated with additives for the molten metal and an organic binder which decomposes into gaseous products in the molten metal. The generated gas stirs the molten metal and thus uniformly incorporates the added components throughout the molten metal.
U.S. Pat. No. 3,729,309 to Kawawa also discloses a method for adding alloying elements in the form of a wire rod to molten metals. The rod has a controlled size and is added to a molten metal bath by inserting it at a controlled speed, so as to produce a refined and purified metal alloy.
The above methods of adding alloying elements to molten metal work fairly well with alloying elements which dissolve and disperse easily in the molten metal. However, such methods do not work so well with elements having limited liquid solubility such as Pb, Bi and Sn and high oxidizing potential such as Mg and Zn.
U.S. Pat. No. 3,947,265 to Guzowski et al proposes a solution to the problem of adding such "hard-to-alloy" materials to molten metal. The process employs a high current arc which is formed between the molten base metal and the alloying addition. The alloying addition is passed through the arc where it is melted and converted into a spray of finely divided superheated molten particles. In such a condition, the particles are able to rapidly dissolve in the molten metal upon contact therewith. While the Guzowski concept of alloying is certainly an interesting one, a need still exists for a process capable of providing improved results.
Accordingly, an object of the present invention is to provide an improved process for adding "hard-to-alloy" alloying materials to molten metals.
Another object of the present invention is to provide an alloying process having high dissolution rates.
Another object of the present invention is to provide an alloying process which is amenable to continuous casting processes.
Another object of the present invention is to provide a lead alloyed, aluminum based metal article having high machinability.
Another object of the present invention is to provide a process for adding alloying material to a molten media that additionally adds heat to the molten media.
Additional objects and advantages of the present invention will become apparent to persons skilled in the art from the following specification and drawings.